Computer users employ writable and rewritable optical discs for a variety of different purposes. They may save programs or data to the discs, for archival or distribution purposes. In the case of CD-type discs, users may make music CD's that can be played in audio CD players, or save music data files to the CD's, such as MP3 files, that can be played in special-purpose CD players. In the case of DVD-type discs, users have greater storage capacity available to them than with CD-type discs, and may be able to make video DVD's that can be played in stand-alone DVD players.
Many types of optical discs include a data side and a label side. The data side is where the data is written to, whereas the label side allows the user to label the optical disc. Unfortunately, labeling can be an unprofessional, laborious, and/or expensive process. Markers can be used to write on optical discs, but the results are decidedly unprofessional looking. Special pre-cut labels that can be printed on with inkjet or other types of printers can also be used, but this is a laborious process: the labels must be carefully aligned on the discs, and so on. Special-purpose printers that print directly on the discs may be used, but such printers are fairly expensive. In the patent application entitled “Integrated CD/DVD Recording and Label” filed on Oct. 11, 2001, and assigned Ser. No. 09/976,877, a solution to these difficulties is described, in which a laser is used to label optical discs.
When optically writing on either the optically writable data or label side of an optical disc, a coordinate system is used to specify positions on the optical disc. Most common is a polar coordinate system, in which two coordinates are used to specify a given position: a radius coordinate, and an angular coordinate. However, such a coordinate system does not map directly to the geometry of the optical disc. That is, different positions on the optical disc may need different degrees of precision among the coordinates to particularly specify the positions. For instance, as the radius coordinate increases, increasingly precise angular coordinates are usually needed to specify uniformly spaced positions on the optical disc, potentially making writing to the optical disc difficult. Previous attempts to potentially solve this problem have utilized Cartesian coordinate systems. However, mapping the geometry of an optical disc to a rectangular, x-y coordinate system can require significant reworking of optical disc devices, making this solution less than desirable.